Reconfigurable optical space switch

ABSTRACT

A method and switch are provided for reconfigurable optical space switch. The method includes receiving a control signal, from a controller, to configure a path through the reconfigurable optical space switch. The method also includes applying a voltage to one or more direction changing devices at each intersection between each of the east-west optical waveguides and each of the north-south optical waveguides to form the path through the reconfigurable optical space switch. The method additionally includes receiving an optical signal in one of a plurality of passive waveguides at a beginning of the path, including the plurality of east-west optical waveguides and the plurality of north-south optical waveguides. The method further includes outputting the optical signal out on of the plurality of passive waveguides at an end of the path.

RELATED APPLICATION INFORMATION

This application claims priority to 62/466,505, filed on Mar. 3, 2017,incorporated herein by reference herein its entirety. This applicationis related to an application entitled “Optically-Secured AdaptiveSoftware-Defined Optical Sensor Network Architecture”, and which isincorporated by reference herein in its entirety. This application isrelated to an application entitled “Transmitter/Receiver with OrbitalAngular Momentum Based Optical Encryption”, and which is incorporated byreference herein in its entirety.

BACKGROUND Technical Field

The present invention relates to optical switches and more particularlyto reconfigurable optical space switches.

Description of the Related Art

Distributed sensor networks have revolutionized sensing with numerousapplications. However, the existing sensor networks, including opticalswitches, are costly and it is impossible to build separate sensornetworks for different applications including environment monitoring,structural damages, tsunami effects, disaster handling and management,security issues, etc. In disaster situations, a wide range ofinformation is obtained from many sensors and that information isemployed to re-route traffic, reconfigure sensor networks to provide ina timely manner the required information for first responders anddecision makers and consequently fix the problem at hand.

SUMMARY

According to an aspect of the present principles, reconfigurable opticalspace switch is provided. The switch includes a plurality of passivewaveguides to transmit optical signals, including a plurality of east(E)-west (W) optical waveguides and a plurality of north (N)-south (S)optical waveguides. The switch also includes one or more directionchanging devices at each intersection between each of the east-westoptical waveguides and each of the north-south optical waveguidesconfigurable to alter a path of an optical signal along one or more ofthe plurality of passive waveguides.

According to another aspect of the present principles, a method isprovided for a reconfigurable optical space switch. The method includesreceiving a control signal, from a controller, to configure a paththrough the reconfigurable optical space switch. The method alsoincludes applying a voltage to one or more direction changing devices ateach intersection between each of the east-west optical waveguides andeach of the north-south optical waveguides to form the path through thereconfigurable optical space switch. The method additionally includesreceiving an optical signal in one of a plurality of passive waveguidesat a beginning of the path, including the plurality of east-west opticalwaveguides and the plurality of north-south optical waveguides. Themethod further includes outputting the optical signal out on of theplurality of passive waveguides at an end of the path.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 shows a block diagram of software-defined optical sensor network,in accordance with the present principles;

FIG. 2 shows a block diagram of vertical-cavity surface-emitting laserreceiver, in accordance with the present principles;

FIG. 3 shows a block diagram of reconfigurable optical space switch, inaccordance with the present principles;

FIG. 4 shows a diagram of an active vertical coupler operationprinciple, in accordance with the present principles;

FIG. 5 shows a block diagram of active vertical coupler basedreconfigurable optical space switch, in accordance with the presentprinciples;

FIG. 6 shows a block diagram illustrating an optical divisionmultiplexing-based passive sensor network employing Slepian-fiber Bragggratings, in accordance with the present principles;

FIG. 7 shows a block diagram illustrating an orbital angularmomentum-based all-optical transmitter, in accordance with the presentprinciples;

FIG. 8 shows a block diagram illustrating an orbital angular momentum(OAM)-based all-optical receiver for OAM decryption, in accordance withthe present principles;

FIG. 9 shows a block diagram illustrating an orbital angular momentummultiplexing for optical sensors, in accordance with the presentprinciples;

FIG. 10 shows a block diagram of a computer processing system, to beused to reconfigure the ROSS or for control purposes, in accordance withthe present principles;

FIG. 11 shows a flow diagram illustrating a method for reconfiguringoptical sensor networks, in accordance with the present principles;

FIG. 12 shows a flow diagram illustrating a method for reconfiguringoptical space switches, in accordance with the present principles; and

FIG. 13 shows a flow diagram illustrating a four-dimensionalmultiplexing method for optical networks, in accordance with the presentprinciples.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In accordance with one embodiment, an adaptive software-defined opticalsensor network (SDOSN) architecture capable of hosting programmablesensors ranging from several thousand to several million is provided.The sensing process is low cost, but highly accurate and capable ofclosely approaching the optical channel capacity. The SDOSN architectureis interoperable with existing optical networks infrastructure. Existingdark fibers can be used together with the currently used fiberinfrastructure. Additionally, the DSOSN is programmable at runtime tochange sensor network topology, active sensors, and their functions toaccommodate current sensor network objectives and applications. TheDSOSN is cost-effective and leverages the emerging virtual networktechnologies and software defined network paradigms.

In one embodiment, the nodes in SDOSN can be bidirectional sensor nodescomposed of an optical transmitter, an optical receiver, and a sensordevice integrated on the same chip. The SDOSN enables sensor networks tobe adaptive to time-varying conditions and reconfigurable to specificobjectives or applications. The SDOSN building modules/subsystems caninclude, e.g.: (i) microelectromechanical system-based (MEMS-based)reconfigurable optical space switch, which can be configured to operateas either unidirectional or bidirectional, capable of switching thewavelength band; (ii) hybrid optical sensor physical network organizedin optical star topology with individual branches being optical fiberlinks operating as the optical buses; and (iii)unidirectional/bidirectional sensor nodes. To support high flexibilityin terms of number of sensor nodes ranging from several thousand toseveral million, four-dimensional multiplexing is employed that includestime-, wavelength-, orbital angular momentum-, and optical basisfunctions-dimensions. Even with moderate requirements with respect tothe number of discrete levels in each dimension, e.g., (>31), severalmillion of sensor nodes can be supported. Fiber Bragg gratings (FBGs)with orthogonal impulse responses can be employed as optical basisfunctions. The class of Slepian sequences, which are mutually orthogonalregardless of the sequence order, can be employed to target mutuallyorthogonal FBG-impulse responses. These Slepian sequences based FBGs canbe employed not only as an additional degree of freedom fororthogonal-division multiplexing, but also to provide all-opticalencryption of high importance in the optically secured, adaptive SDOSN.Additionally, the orbital angular momentum (OAM) can be employed as anadditional degree of freedom (DOF) with the purpose to, e.g.: (i) tosecure sensor data and (ii) provide a new DOF, OAM multiplexing, tosupport a larger number of sensor nodes.

The impact of this approach will be to allow accurate, adaptive,run-time reconfigurable high-density optical sensor networks to beincorporated into existing state-of-the-art optical networks. This canresult in a scalable, flexible and cost-effective sensor networks thatcan support millions of sensing nodes that can be programmed at runtimeto accommodate a wide range of applications and objectives. Thefour-dimensional (4-D) approach scales well to an ultra-high density ofsensors (even several millions), while employing moderate number ofdiscrete levels per dimension, by using bidirectional sensor nodes thatare low-cost, energy-efficient, bandwidth-efficient, and which requirelow maintenance; combined with the optical sensor network topology andreconfigurable photonic space switch. The SDOSN can provide all-opticalencryption capability and thus the sensor readout information cannot becompromised by an un-authorized user. The secure sensor readoutinformation can be employed to control an operation of a processor-basedmachine responsive to the sensor readout information, e.g., sounding analarm, issuing a weather emergency alert, disabling power in a floodingsituation, etc.

Embodiments described herein may be entirely hardware, entirely softwareor including both hardware and software elements. In a preferredembodiment, the present invention is implemented in software, whichincludes but is not limited to firmware, resident software, microcode,etc.

Embodiments may include a computer program product accessible from acomputer-usable or computer-readable medium providing program code foruse by or in connection with a computer or any instruction executionsystem. A computer-usable or computer readable medium may include anyapparatus that stores, communicates, propagates, or transports theprogram for use by or in connection with the instruction executionsystem, apparatus, or device. The medium can be magnetic, optical,electronic, electromagnetic, infrared, or semiconductor system (orapparatus or device) or a propagation medium. The medium may include acomputer-readable storage medium such as a semiconductor or solid statememory, magnetic tape, a removable computer diskette, a random accessmemory (RAM), a read-only memory (ROM), a rigid magnetic disk and anoptical disk, etc.

Each computer program may be tangibly stored in a machine-readablestorage media or device (e.g., program memory or magnetic disk) readableby a general or special purpose programmable computer, for configuringand controlling operation of a computer when the storage media or deviceis read by the computer to perform the procedures described herein. Theinventive system may also be considered to be embodied in acomputer-readable storage medium, configured with a computer program,where the storage medium so configured causes a computer to operate in aspecific and predefined manner to perform the functions describedherein.

A data processing system suitable for storing and/or executing programcode may include at least one processor coupled directly or indirectlyto memory elements through a system bus. The memory elements can includelocal memory employed during actual execution of the program code, bulkstorage, and cache memories which provide temporary storage of at leastsome program code to reduce the number of times code is retrieved frombulk storage during execution. Input/output or I/O devices (includingbut not limited to keyboards, displays, pointing devices, etc.) may becoupled to the system either directly or through intervening I/Ocontrollers.

Network adapters may also be coupled to the system to enable the dataprocessing system to become coupled to other data processing systems orremote printers or storage devices through intervening private or publicnetworks. Modems, cable modem and Ethernet cards are just a few of thecurrently available types of network adapters.

Referring now in detail to the figures in which like numerals representthe same or similar elements and initially to FIG. 1, a block diagram ofsoftware-defined optical sensor network 100 (SDOSN) is illustrativelydepicted in accordance with one embodiment of the present principles. Inone embodiment, the SDOSN building modules/subsystems, as shown in FIG.1, can include: (i) MEMS-based reconfigurable optical space switch 30(ROSS), which can be configured to operate as either unidirectional orbidirectional, capable of switching the wavelength band; (ii) hybridoptical sensor physical network organized in optical star topology withindividual branches with optical tap couplers 18 being optical fiberlinks operating as the optical buses and an optical star coupler 20; and(iii) unidirectional/bidirectional sensor nodes with configuration ofbidirectional sensor node 10.

In one embodiment, the sensor node 10 can include a sensor device 12.The sensor device 12 can include more than one type of sensor, e.g.,current sensors, voltage sensors, light sensors, seismic sensors,chemical sensors, smoke sensors, carbon monoxide sensors, air pollutionsensors, electrochemical gas sensors, flow sensors, radiation sensors,pressure sensors, optical sensors, and temperature sensors. The sensornode 10 can include an optical transmitter 16 and an optical directdetection receiver 14 that are connected with an optical tap coupler 18.The optical transmitter 16 and the optical direct detection receiver 14can communicate with the sensor device 12 in the sensor node 10.

To support high flexibility in terms of number of sensor nodes 10ranging from several thousands to several millions, four-dimensionalmultiplexing can be employed including time-, wavelength-, OAM, andoptical basis functions-dimensions. Even with moderate requirements withrespect to the number of discrete levels in each dimension, e.g., (>31),several million sensor nodes can be supported. The FBGs with orthogonalimpulse responses, can be employed as the optical basis functions, canbe designed and fabricated. The class of Slepian sequences, which aremutually orthogonal regardless of the sequence order, can be employed asthe target FBG-impulse responses. These Slepian sequences based FBGswill can be employed not only as an additional degree of freedom fororthogonal-division multiplexing, but also to provide all-opticalencryption of high importance in the optically secured, adaptive SDOSN.Alternatively, complex-basis functions can be used as impulse responsesof corresponding FBGs.

To enable the bidirectionality, in addition to bidirectional sensor node10 shown in FIG. 1, a vertical-cavity surface-emitting laser(VCSEL)-based bidirectional sensor node can be employed. As with anykind of laser, VCSELs are usually considered as optical transmitters.However, VCSELs can operate also as optical receivers for high bandwidthamplitude modulated signals.

Referring now to FIG. 2, a block diagram of vertical-cavitysurface-emitting laser receiver is illustratively depicted in accordancewith an embodiment of the present principles. A vertical-cavitysurface-emitting laser receiver can be realized by injection-locking(IL) the VCSEL 210 to the receiving signal as illustrated in FIG. 2:once the IL is established, the modulation can be extracted directly bythe VCSEL through its bias current. On the other end, operating in a lowinjection ratio regime, single-mode VCSELs can be employed to performdirect detection of the phase information carried by an optical signal.This approach is particularly useful for optical sensor networkapplications because it provides for high-linearity and multileveltransmission without the need of more complex coherent receivers. Themode of operation can be changed by changing the bias voltage polarityof the VCSEL. A solar cell-based battery supply for the VCSEL can beemployed to extend the life-time of the VCSEL.

Referring now to FIG. 3, a block diagram of reconfigurable optical spaceswitch 300 (ROSS) is illustratively depicted in accordance with anembodiment of the present principles. Consider the reconfiguration ofthe microelectromechanical system-mirrors-based active switch,illustrated in FIG. 3. To simplify the description of ROSS 300reconfiguration, assume that the number of ports at each side of theswitch is fixed to N. The ROSS architecture is based on an N×N grid,wherein there are 4N ports. Each port can serve either as an input oroutput. The grid consists of N² switching cells. The four sides of theswitch and the four sides of a switching cell are referred to as North(N), East (E), South (S), and West (W). The state of a switching cellmay be in any one of the three switching states: (1) NS-EW; (2) NE-SW;and (3) NW-SE; with traffic being bidirectional. The key differences ofthe ROSS architecture with respect to that of the crossbar switch can besummarized as follows. (i) A crossbar switch of size 4N×4N would utilize16N² switching cells, each with two states of operation. Alternately,the architecture utilizes only N² switching cells with three switchingstates per switching cell. (ii) A crossbar switch is non-blocking;however, the ROSS architecture is blocking. To compensate for theblocking nature, the architecture provides the flexibility of realizinga given set of connections in many different ways. For full switchingcapability of the switching cell, two MEMS 310 are needed for E-N andE-S traffic, and two MEMS 310 for W-S and W-N traffic, as illustrated inFIG. 3. The switch can be operated also with only two highly-flexibleMEMS-mirrors per switching cell, but will not be able to supportfull-duplex operation of the ROSS 300, which is typically not needed inoptical sensor networks.

MEMS-mirrors based configuration time is in the order of severalmicro-seconds (μs). For certain, applications, the ROSS 300 should beoperated in the order of several nano-seconds (ns). For theseapplications, the switch can be implemented by employing an activevertical coupler (AVC)-based ROSS as follows. The AVCs-based opticalswitch was initially fabricated in quaternary semiconductor multilayersdeposited on an InP substrate. Some unique properties, include ultralowcrosstalk, e.g., (67 dB), very high ON-OFF contrast ratio, e.g., (70dB), about 1 nano-second (ns) switching time, and lossless switchingoperation. The switching of optical signals exceeding 10 Gb/s has beendemonstrated.

Referring now to FIG. 4, a diagram of an active vertical coupleroperation principle 400 is illustratively depicted in accordance with anembodiment of the present principles. The switching cell of the switch,shown in FIG. 4, consists of two perpendicular groups of passive ridgewaveguides 410 that form the input and output waveguides. Two ActiveVertical Couplers (AVCs) 420 are formed at each cross-point by placingan active waveguide coupler stacked on top of both the input and outputpassive waveguides 410. A Total Internal Reflection (TIR) mirror cutsvertically through the active waveguide and diagonally across thewaveguide intersection. This allows a 90° redirection of the opticalsignal from the first AVC 420 to the second one. In the ON state (in thepresence of applied voltage), the applied voltage alters the refractiveindices of AVC 420 and lower waveguides allowing the redirection of thelight for 90°. The signal is reflected by the TIR, and then coupled fromthe upper waveguide to the output waveguide in the second AVC. Atransient metal oxide material, whose index of refraction is latchable,can be employed for the AVC. In other words, once the applied voltageturns the AVC 420 on, the coupling structure remains stable withoutapplying the voltage further. In the OFF state, the AVC 420 structure iserased by changing the polarity of the applied voltage. The effectiverefractive index of the upper waveguide is significantly different fromthat of the input and the output passive waveguides 410, resulting invery low coupling, and the input signal is forwarded to the nextswitching cell along the passive waveguide 410. A metal-oxide-metalstructure, specifically, transition-metal-oxide materials sandwichedbetween noble metal electrodes, can be employed. A non-linear devicenamed Memrister can be employed, the Memrister can include a nano-scalePt—TiO₂—Pt structure, and exhibiting a non-linear current voltageresponse as well as a latching of resistivity by altering polarity ofthe applied voltage. A ROSS using this technology will only consumeenergy to change the switch state; once changed the ROSS will notconsume energy to stay in that state. Alternatively, InGaAsP—InPtechnology, can also be employed.

Referring now to FIG. 5, a block diagram of active vertical couplerbased reconfigurable optical space switch 500 is illustratively depictedin accordance with an embodiment of the present principles. For fullswitching capability of the cell, two top and two bottom electrodes areneeded, as illustrated in FIG. 5. The switching cells are furthercombined to form 2(c+r) ports ROSS, where c denotes number of switchingcells per column, while r denotes the number of switching cells per row.The dashed-AVCS 530 are placed on the top of corresponding waveguidecrosses, while the dotted-AVCs 520 on the bottom. The design has manyfeatures including: (i) the switch is bidirectional with the oppositedirection data streams using different wavelengths; (ii) the switch has2(c+r) ports; (iii) the switch allows full connectivity; (iv) theswitching operation is latchable. While designing an ROSS matrix, thetransmission characteristics can be optimized over the entire ROSS sothat the quality of signals transmitted via the shortest and longestpaths in the matrix are comparable. The wavelength paths (optical links)in the switch are bidirectional. The ROSS can employ 2W wavelengths{λ_(l), λ _(l), . . . , λ_(w), λ _(w)}, where λ_(i) (i=1, 2, . . . , W)wavelengths are used for west-to-east and north-to-south traffic and λ_(i) for the opposite direction traffic. The ROSS can be suitable forintegration in large interconnects by appropriately combining the smallswitches. The main issues related to building large interconnectsinclude the number of required small switches, uniform attenuation ofdifferent optical paths (which is not an issue when ROSS is employed),the number of crossovers, and blocking characteristics.

Four-dimensional (4-D) multiplexing can be employed, as indicated above,to support several million sensors including wavelength-divisionmultiplexing (WDM), time-division multiplexing (TDM), optical divisionmultiplexing (ODM), and OAM multiplexing. The ODM can be based on FBGswhose impulse responses are Slepian sequences. The Slepian sequences{s_(n) ^((j))(N, W)} of the j-th order (j=0, 1, 2, . . . ) are mutuallyorthogonal sequences for sequence length N and discrete bandwidth W, andcan be determined as a real-valued solution of the following system ofdiscrete equations:ΣE _(i=0) ^(N−1){sin [2π(n−i)]/[π(n−i)]}s _(n) ^((j))(N,W)=μ_(j)(N,W)s_(n) ^((j))(N,W),where i and n denote the particular samples in each Slepian sequence,while the shaping factors μ_(j)(N, W) are ordered eigenvalues. Thediscrete layer-peeling algorithm (DLPA) has proven to be efficient toolfor designing fiber Bragg gratings (FBGs) with a desired transferfunction, and this method can be employed to design FBGs having Slepiansequences for impulse responses, called here Slepian-FBGs. However,given the fact that DLPA is performed in spectral domain it faces thefinite resolution problem, which results in reduced cardinality Slepiansequences set for a given tolerable cross-correlation coefficient ρ, inparticular for non-zero laser pulse-widths. Moreover, given thefabrication limitations, this problem will be even more pronouncedduring the fabrication process. To overcome this problem, the Bragggratings are designed to have orthogonal impulse responses by means ofthe time-domain (TD) based FBG design algorithm. Compared to DLPA, thecorresponding TD design algorithm results in FBG designs with impulseresponses perfectly matched to the target Slepian sequences, and thusproviding the full cardinality of the set of Slepian sequences.Slepian-FBGs can be employed to provide the third multiplexing dimensionrequired, namely, optical-division multiplexing (ODM). To secure thesensor collected data, an all-optical encryption scheme based onSlepian-FBGs can be employed. Alternatively, complex basis functions canbe used as impulse responses of corresponding FBGs.

Referring now to FIG. 6, a block diagram of an optical divisionmultiplexing-based passive sensor network 600 employing Slepian-fiberBragg gratings is illustratively depicted in accordance with anembodiment of the present principles. In one embodiment, the opticaldivision multiplexing-based passive sensor network employingSlepian-fiber Bragg gratings can include a laser diode 610 that may feedinto a circulator 620, with ports 1, 2, and 3 and operation directions1-2 and 2-3. The circulator 620 can have a bi-directional optical fiber,connected to port 2, with a chain of one or more Slepian-FBGs 640. Thechain of Slepian-FBGs can be used in SDOSN architecture shown in FIG. 1.The circulator 620 output 3 passes the reflected signals from FBGstrough fiber and then towards tunable complex-conjugate Slepian-FBG n630, used to select the signal originated from the n-the Slepian-FBG,caring the optical sensing information originating from the n-th sensor,and forwards it to a photodetector 635. This concept is applicable toboth active and passive sensor networks. Since impulse responses ofSlepian-FBGs are mutually orthogonal, all FBGs operate on the samewavelength. In this particular configuration, Slepian-FBGs must befabricated on such a way to be 50% reflective (and 50% transparent).

Another approach to secure the data collected by sensor is to employ theorbital angular momentum (OAM) as a degree of freedom. The pure OAMmodes can be generated with the help spatial light modulators (SLMs),and SLMs are defined as ϕ_(n)=exp(jnϕ); n=0, ±1, ±2, . . . , and satisfythe orthogonality principle because the dot-product is

$\left\langle \phi_{m} \middle| \phi_{n} \right\rangle = {{\frac{1}{2\pi}{\int_{0}^{2\pi}{e^{{- {jm}}\;\phi}e^{{jn}\;\phi}d\;\phi}}} = \left\{ {\begin{matrix}{1,{n = m}} \\{0,{n \neq m}}\end{matrix} = {\delta_{n\; m}.}} \right.}$

Given that OAM-based basis functions are mutually orthogonal they can beused as the basis functions for either OAM multiplexing ormultidimensional signaling as well as to improve the physical-layersecurity. The concern is when employing the OAM degree of freedom forall-optical encryption. The simplest mathematical expression of an OAMmode and zero-order Gaussian beam with an incidence angle θ can bewritten, respectively, asu(r,ϕ,z)=exp(−jmϕ)exp(−jkz) and u ₀=exp(jk×sin θ)exp(−jkz)where k is the wave number and z is the propagation axis. A computergenerated hologram (CGH), which will be recorded on a proper polymermaterial, represents the interference pattern between two incidentbeams, in this case a zero-order Gaussian beam and a beam to begenerated. The resulting intensity I interference pattern, assuming thatz=0 can be expressed asI=|u(r,ϕ,z=0)+u ₀|²=2+2 cos(k×sin θ−mϕ).

This sinusoidal grating pattern is easy to generate but with lowdiffraction efficiency. It is well-known that blazed grating can obtain100% diffraction efficiency, whose interference pattern can be expressedas I=k×sin θ−mϕ mod 2π.

Referring now to FIGS. 7 and 8, a block diagram of an orbital angularmomentum-based all-optical transmitter and a block diagram of an orbitalangular momentum-based all-optical transmitter are illustrativelydepicted in accordance with an embodiment of the present principles.FIGS. 7 and 8 describe how OAM modes can be used in both free-spaceoptical (FSO) and multimode fiber (MMF) links, by replacing thesingle-mode fiber links shown in FIG. 1 with either FSO or MMF links.This scheme employs the following N=2K+1 OAM modes {−K, . . . −1, 0, 1,. . . , K}. The orbital angular momentum-based all-optical transmittercan be composed of encryption stage 710 and masking stage 728. Theencryption stage 710 can include an optical switch 712, the opticalswitch 712 can randomly select the branch imposing non-negative OAMindex basis functions. The encryption stage 710 can take user data 704through an optical transmitter 708 as an input of the optical switch712. The optical switch 712 can output fibers/waveguides to a powercombiner 720. The optical switch 712 can output directly to the powercombiner 720, corresponding to zeroth OAM mode, or through one or moreCGH elements 716, corresponding to positive indices OAM modes.

The masking stage 728 can include an optical switch 713, the opticalswitch 713 can randomly select the branch with negative OAM index basisfunction. The masking stage 728 can take a random sequence or noisysequence 722 through an optical transmitter 708 as an input of theoptical switch 713. The optical switch 713 output goes through one ormore CGH elements 716 on the way to the power combiner 720,corresponding to negative indices OAM modes. In the masking stage 728,the samples from complex Gaussian random generator are generated. Thepurpose of this stage is to add the Gaussian noise so that any datastructure is lost in both time- and frequency-domains, providing,therefore, stealth or covert communication capability. Since theadditive noise is imposed on orthogonal OAM basis functions, thede-masking stage is not needed on the receiver side. The output from theencryption stage 710 and the masking stage 728 can be combined in apower combiner 724 to produce the output from the transmitter.

The orbital angular momentum-based all-optical receiver for OAMdecryption can include an OAM demultiplexer 805. The OAM demultiplexer805 can include a power splitter 810 that can take an input signal andsplit the signal to send to one or more coherent optical detectors 840.The one or more coherent optical detectors 840 feed into a select thelargest input circuit 870 which outputs the largest input. One or morethe signals from the power splitter 810 can pass through a CGH*(*-operation denotes complex conjugation) element 820 before the one ormore coherent optical detectors 840. The output of each CGH* element 820in the OAM demultiplexer 805 represents the projection along thecorresponding OAM basis function with nonnegative OAM indices. Sinceonly one OAM mode is used in encryption stage, only the correct complexconjugate OAM basis function will generate strong peak, the otheroutputs will generate just noisy signals. Therefore, the select thelargest input circuit 870 selects the strongest output and can beemployed to identify the correct branch. A single local laser is usedfor all coherent optical detectors. Alternatively, for OAM decryptionpurposes, OAM demultiplexer can be replaced with reconfigurablecomplex-conjugate Cal detecting the desired OAM mode n. In this case,only single coherent detector is needed, while select the largest inputcircuit is not needed. For OAM demultiplexing purposes only (withoutoptical encryption), the select the largest input module 870 is notneeded.

Referring now to FIG. 9, a block diagram of an orbital angular momentummultiplexing for optical sensors is illustratively depicted inaccordance with an embodiment of the present principles. In addition toall-optical encryption, OAM multiplexing can be used to provide even thefourth dimension for multiplexing, namely, OAM multiplexing, which isillustrated in FIG. 9. This scheme can support up to N optical sensorper single wavelength. The laser diode 905 signal is split intoN-branches by a power splitter 910, such as 1:N optical star. In n-thbranch OAM mode n is imposed by CGH element 915 n. Each CGH element 915feed into an optical sensor 930 followed by an OAM detection 945 and aphotodetector 960. After sensing is completed, a conversion is performedof OAM modes to Gaussian modes to detect the sensed signals. Byemploying the time-division multiplexing, each branch can support Ttime-domain sensors. Further, by employing W wavelength sources, intotal NTW sensors can be supported. Given that MMF or FSO links areused, the OAM multiplexing based sensor networks can support the bustopology as well. In that case, each optical sensor node will containthe corresponding CGH device. Finally, by employing L ODM approach, intotal NTWL sensors can be supported. For instance, by settingN=T=W=L=50, 6.25 million sensor for reasonable number of discrete levelsin each multiplexing dimension can be supported.

An adaptive software-defined optical sensor network (SDOSN) architecturethat is capable of hosting programmable sensors ranging from severalthousand to several millions is provided. Sensing process is of lowcost, but highly accurate and capable of closely approaching the opticalchannel capacity. The SDOSN architecture is interoperable with existingoptical networks infrastructure. The SDOSN can be programmable atruntime to change sensor network topology, active sensors, and theirfunctions to accommodate current sensor network objectives andapplications. The sensor network can be cost-effective and leverages theemerging virtual network technologies and software defined networkparadigms.

In one embodiment, the nodes in SDOSN can be bidirectional sensor nodescomposed of optical transmitter, optical receiver, and sensor deviceintegrated on the same chip. The SDOSN enables sensor networks to beadaptive to time-varying conditions and reconfigurable to specificobjectives or applications. The SDOSN building modules/subsystems caninclude, e.g.: (i) MEMS-based reconfigurable optical space switch, whichcan be configured to operate as either unidirectional or bidirectional,capable of switching the wavelength band; (ii) hybrid optical sensorphysical network organized in optical star topology with individualbranches being optical fiber links operating as the optical buses; and(iii) unidirectional/bidirectional sensor nodes. To support highflexibility in terms of number of sensor nodes ranging from severalthousand to several millions, four-dimensional multiplexing can beemployed that includes time-, wavelength-, optical basis functions-, andOAM basis functions-dimensions. Even with moderate requirements withrespect to the number of discrete levels in each dimension, e.g., (>31),several millions of sensor nodes can be supported. The FBGs withorthogonal impulse responses can be employed as the optical basisfunctions. The class of Slepian sequences, which are mutually orthogonalregardless of the sequence order, can be employed as the target mutuallyorthogonal FBG-impulse responses. These Slepian sequences based FBGs canbe employed not only as an additional degree of freedom fororthogonal-division multiplexing, but also to provide all-opticalencryption of high importance in the optically secured, adaptive SDOSN.Additionally, the orbital angular momentum (OAM) can be employed as anadditional degree of freedom (DOF) with the purpose to: (i) to securesensor data and (ii) provide a new DOF, OAM multiplexing, to support alarger number of sensor nodes.

Referring now to FIG. 10, a block diagram of a computer processingsystem 1000, to be used to reconfigure the ROSS or for control purposes,is illustratively depicted in accordance with an embodiment of thepresent principles. The computer system 1000 includes at least oneprocessor (CPU) 1005 operatively coupled to other components via asystem bus 1002. A cache 1006, a Read Only Memory (ROM) 1008, aRandom-Access Memory (RAM) 1010, an input/output (I/O) adapter 1020, asound adapter 1030, a network adapter 1070, a user interface adapter1050, and a display adapter 1060, are operatively coupled to the systembus 1002.

A first storage device 1022 and a second storage device 1029 areoperatively coupled to system bus 1002 by the I/O adapter 1020. Thestorage devices 1022 and 1029 can be any of a disk storage device (e.g.,a magnetic or optical disk storage device), a solid state magneticdevice, and so forth. The storage devices 1022 and 1029 can be the sametype of storage device or different types of storage devices.

A speaker 1032 may be operatively coupled to system bus 1002 by thesound adapter 1030. A transceiver 1075 is operatively coupled to systembus 1002 by network adapter 1070. A display device 1062 is operativelycoupled to system bus 1002 by display adapter 1060.

A first user input device 1052, a second user input device 1059, and athird user input device 1056 are operatively coupled to system bus 1002by user interface adapter 1050. The user input devices 1052, 1059, and1056 can be any of a sensor, a keyboard, a mouse, a keypad, a joystick,an image capture device, a motion sensing device, a power measurementdevice, a microphone, a device incorporating the functionality of atleast two of the preceding devices, and so forth. Of course, other typesof input devices can also be used, while maintaining the spirit of thepresent invention. The user input devices 1052, 1059, and 1056 can bethe same type of user input device or different types of user inputdevices. The user input devices 1052, 1059, and 1056 are used to inputand output information to and from system 1000.

Of course, the computer system 1000 may also include other elements (notshown), as readily contemplated by one of skill in the art, as well asomit certain elements. For example, the devices described in FIGS. 2, 3,5, 7, and 8 can be controlled by computer system 1000. For example,various other input devices and/or output devices can be included incomputer system 1000, depending upon the particular implementation ofthe same, as readily understood by one of ordinary skill in the art. Forexample, various types of wireless and/or wired input and/or outputdevices can be used. Moreover, additional processors, controllers,memories, and so forth, in various configurations can also be utilizedas readily appreciated by one of ordinary skill in the art. These andother variations of the computer system 1000 are readily contemplated byone of ordinary skill in the art given the teachings of the presentinvention provided herein.

Moreover, it is to be appreciated that network 100 and network 600described above with respect to FIG. 1 and FIG. 6 are networks forimplementing respective embodiments of the present invention. Part orall of computer processing system 1000 may be implemented in one or moreof the elements of network 100 and/or one or more of the elements ofnetwork 600.

Further, it is to be appreciated that computer processing system 1000may perform at least part of the method described herein including, forexample, at least part of method 1100 of FIG. 11 and/or at least part ofmethod 1200 of FIG. 12 and/or at least part of method 1300 of FIG. 13.

Referring now to FIG. 11, a flow diagram of a method performed inreconfigurable optical sensor network is illustratively depicted inaccordance with an embodiment of the present principles. In block 1110,configure, by a controller, the reconfigurable optical sensor network,including one or more reconfigurable optical space switches, for a typeof sensor data. In block 1120, generate sensor data in the type ofsensor data with one or more of a plurality of bidirectional sensors. Inblock 1130, send the sensor data to one or more optical star couplers.In block 1140, forward the sensor data from one of the one or moreoptical star couplers to the one of one or more reconfigurable opticalspace switches.

Referring now to FIG. 12, a flow diagram of a method 1200 in areconfigurable optical space switch is illustratively depicted inaccordance with an embodiment of the present principles. In block 1210,receive a control signal, from a controller, to configure a path throughthe reconfigurable optical space switch. In block 1220, apply a voltageto one or more direction changing devices at each intersection betweeneach of the east-west optical waveguides and each of the north-southoptical waveguides to form the path through the reconfigurable opticalspace switch. In block 1230, receive an optical signal in one of aplurality of passive waveguides at a beginning of the path, includingthe plurality of east-west optical waveguides and the plurality ofnorth-south optical waveguides. In block 1240, output the optical signalout on of the plurality of passive waveguides at an end of the path.

Referring now to FIG. 13, a flow diagram of a four-dimensionalmultiplexing method 1300 for optical networks is illustratively depictedin accordance with an embodiment of the present principles. In block1310, receive sensor data to be transmitted on an optical network. Inblock 1320, encode the sensor data into an optical signal employing oneor more multiplexing systems. In block 1330, send the sensor data to oneor more optical star couplers. In block 1340, decode the optical signalinto the sensor data employing the one or more multiplexing systems. Inblock 1350, control an operation of a processor-based machine responsiveto the sensor data.

The foregoing is to be understood as being in every respect illustrativeand exemplary, but not restrictive, and the scope of the inventiondisclosed herein is not to be determined from the Detailed Description,but rather from the claims as interpreted according to the full breadthpermitted by the patent laws. It is to be understood that theembodiments shown and described herein are only illustrative of theprinciples of the present invention and that those skilled in the artmay implement various modifications without departing from the scope andspirit of the invention. Those skilled in the art could implementvarious other feature combinations without departing from the scope andspirit of the invention. Having thus described aspects of the invention,with the details and particularity required by the patent laws, what isclaimed and desired protected by Letters Patent is set forth in theappended claims.

What is claimed is:
 1. A reconfigurable optical space switch,comprising: a plurality of passive waveguides to transmit opticalsignals, including a plurality of east (E)-west (W) optical waveguidesand a plurality of north (N)-south (S) optical waveguides; and one ormore direction changing devices at each intersection between each of theeast-west optical waveguides and each of the north-south opticalwaveguides configurable to alter a path of an optical signal along oneor more of the plurality of passive waveguides, wherein the one or moredirection changing devices support full-duplex operation along thepassive waveguides.
 2. The reconfigurable optical space switch asrecited in claim 1, wherein the one or more direction changing devicesare microelectromechanical system mirrors.
 3. The reconfigurable opticalspace switch as recited in claim 1, wherein the one or more directionchanging devices includes four microelectromechanical system mirrors toenable traffic along E-N, E-S, W-N, and W-S paths.
 4. The reconfigurableoptical space switch as recited in claim 1, wherein the one or moredirection changing devices includes two microelectromechanical systemmirrors.
 5. The reconfigurable optical space switch as recited in claim1, wherein the one or more direction changing devices are activevertical coupler units.
 6. The reconfigurable optical space switch asrecited in claim 5, wherein the active vertical coupler units includetwo active vertical couplers with a total internal reflection mirror. 7.The reconfigurable optical space switch as recited in claim 6, whereinthe active vertical couplers include material with a latcheabie index ofrefraction.
 8. The reconfigurable optical space switch as recited inclaim 6, wherein the total internal reflection mirror enables 90°redirection between the two active vertical couplers.
 9. Thereconfigurable optical space switch as recited in claim 1, wherein theone or more direction changing devices includes active vertical couplerunits on top of the plurality of passive waveguides and two verticalcoupler units on the bottom of the plurality of waveguides.
 10. A methodfor a reconfigurable optical space switch, comprising: receiving acontrol signal, from a controller, to configure a path through thereconfigurable optical space switch; applying a voltage to one or moredirection changing devices at each intersection between each of theeast-west optical waveguides and each of the north-south opticalwaveguides to form the path through the reconfigurable optical spaceswitch; receiving an optical signal in one of a plurality of passivewaveguides at a beginning of the path, including the plurality ofeast-west optical waveguides and the plurality of north-south opticalwaveguides; and outputting the optical signal out on one of theplurality of passive waveguides at an end of the path, wherein the oneor more direction changing devices support full-duplex operation alongthe passive waveguides.
 11. The method as recited in claim 10, whereinthe one or more direction changing devices are microelectromechanicalsystem mirrors.
 12. The method as recited in claim 10, wherein the oneor more direction changing devices includes four microelectromechanicalsystem mirrors to enable traffic along E-N, E-S, W-N, and W-S paths. 13.The method as recited in claim 10, wherein the one or more directionchanging devices includes two microelectromechanical system mirrors. 14.The method as recited in claim 10, wherein the one or more directionchanging devices are active vertical coupler units.
 15. The method asrecited in claim 14, wherein the active vertical coupler units includetwo active vertical couplers and a total internal reflection mirror. 16.The method as recited in claim 15, wherein the active vertical couplersinclude material with a latchable index of refraction.
 17. The method asrecited in claim 15, wherein the total internal reflection mirrorenables 90° redirection between the two active vertical couplers. 18.The method as recited in claim 10, wherein the one or more directionchanging devices includes active vertical coupler units on top of theplurality of passive waveguides and two vertical coupler units on thebottom of the plurality of waveguides.
 19. A reconfigurable opticalspace switch, comprising: a plurality of passive waveguides to transmitoptical signals, including a plurality of east (E)-west (W) opticalwaveguides and a plurality of north (N)-south (S) optical waveguides;and one or more direction changing devices at each intersection betweeneach of the east-west optical waveguides and each of the north-southoptical waveguides configurable to alter a path of an optical signalalong one or more of the plurality of passive waveguides, wherein theone or more direction changing devices includes active vertical couplerunits on top of the plurality of passive waveguides and two verticalcoupler units on the bottom of the plurality of waveguides.